The defense included several future NFL players, including end Corey Wootton and cornerback Sherrick McManis. Eight starters returned, and the unit improved from 88th nationally in points allowed to 26th in Hankwitz's first season.

But something was missing. As Hankwitz surveyed the number of spread offenses in college football -- not to mention the one his defense practiced against every day at Northwestern -- he knew the Wildcats' defense needed a speed boost.

"We had some players with good speed, but as a total defense, we didn't have that same speed at every position," Hankwitz told ESPN.com. "In this day in age with spread offenses, you need to have athletes who have the ability and speed to make plays in space. That's where we were a little deficient at the time. If you had a guy hurt, the next guy might not have been as fast. So we recruited to that end. We tried to recruit better speed to cornerback, and we're making progress in that way.

"As a whole, our team defensive speed has improved, and we're excited about that."

It was noticeable last season as Northwestern's defense improved to 47th nationally after plummeting to 80th the year before. Several younger players who were part of the speed-driven recruiting push played key roles, including defensive backs Ibraheim Campbell and Nick VanHoose, linebacker Chi Chi Ariguzo and linemen Dean Lowry and Deonte Gibson.

Northwestern's speed upgrade on defense has jumped out during spring practice. In Tuesday's workout, Lowry zoomed past a tackle for an easy "sack" against quarterback Trevor Siemian. Speed has helped cornerback Dwight White put himself in position to start opposite VanHoose in the fall. The same holds true for safeties like Traveon Henry, Jimmy Hall and Terrance Brown, competing to start next to Campbell.

"Our team speed is definitely much improved," head coach Pat Fitzgerald said. "Our secondary runs as well as it has at all four positions."

The popularity of the spread offense, which Northwestern has used since 2000, fueled the team's speed push in recruiting. Northwestern needed more athletes who could make plays in space, especially in the secondary.

Not surprisingly, the secondary had the most dramatic upgrade last season, and depth at both cornerback and safety has improved for 2013. The secondary not only has more speed but better size.

"Traveon Henry's a 6-[foot]-1, 200-plus-pound safety, Jimmy Hall's the same way, Terrance Brown is the same way; we've upgraded our size at corner," Fitzgerald said. "Most of our guys used to be 5-foot-9 and 5-foot-10. Now we're 5-11 and 6-foot. That size-speed combination is critically important if we want to take the next step in this league."

Greater speed allows Hankwitz to be "a little more aggressive" with his defensive calls. It also helps younger players get on the field early as they can overcome some weaknesses technically and fundamentally.

"Last year, being a little undersized at D-end as a freshman, I relied on my speed a lot of times to beat tackles," said Lowry, who had a sack, six quarterback hurries and three tackles for loss as a true freshman. "When you're fast, it sets up moves, so if a tackle is overset, you come back with a counter. You've got to make sure you use your technique, use your hands where the coaches teach you. But having the extra speed, it's almost like you can't teach that.

"It's something most guys don't have."

Northwestern's speed push started with the linebackers and spread quickly to the secondary, but the line hasn't been neglected. Redshirt freshman end Ifeadi Odenigbo, the team's most-decorated recruit in years, only started playing football as a high school sophomore but made his mark with speed, twice tracking downBraxton Miller in a playoff game.

Both Odenigbo and Gibson ran track in high school, while both Gibson and Lowry played basketball.

"They're very, very athletic," senior end Tyler Scott said. "Dean's very athletic. Deonte, when he's healthy, is a force coming off the edge. And Ifeadi, he's got some speed that we haven't seen here for a while."

Northwestern's defense expects to be seeing more of that speed in the coming seasons.

"We're still not quite there where we have all five classes at an elite level athletically," Fitzgerald said, "but I think we're really close."